A number of devices have heretofore been utilized for removal, dilation or ablation of occlusive matter from the lumens of blood vessels.
Examples of the types of devices which have heretofore been utilized to dilate, ablate or otherwise remove obstructions from blood vessels include a.) balloon angioplasty catheters which function to radially dilate an occlusive lesion, b.) ultrasound ablation catheters which serve to ultrasonically ablate the occlusive lesion, c.) laser catheters which vaporize or ablate the occlusive lesion by laser energy and d.) atherectomy devices which operate to cut, shave, or grind occlusive matter from the blood vesel lumen using mechanical means.
Examples of ultrasonic ablation devices are described in U.S. Pat. Nos. 3,433,226 (Boyd), 3,823,717 (Pohlman, et al.), 4,808,153 (Parisi), 4,936,281 (Stasz), 3,565,062 (Kuris), 4,924,863 (Sterzer), 4,B70,953 (Don Michael, et al.), 5,069,664 (Suess, et al.) and 4,920,954 (Alliger, et al.), as well as other patent publications W087-05739 (Cooper), W089-06515 (Bernstein, et al.), W090-0130 (Sonic Needle Corp.), EP316789 (Don Michael, et al.), DE 3,821,836 (Schubert), DE2438648 (Pohlman), and EP 0443256A1 (Baruch).
Examples of atherectomy devices include those described in U.S. Pat. No. 5,100,423 (Fearnot) and EP0347098A2 (Shiber).
Although laser ablation, ultrasonic ablation and atherectomy devices have been utilized for ablating or removing occlusive matter from blood vessels, balloon dilation angioplasty remains the most widely utilized interventional technique for nonsurgical restoration of patency in occluded or partially occluded blood vessels. One problem associated with balloon dilation angioplasty is that, in blood vessels which are fully occluded, it is sometimes difficult to penetrate the occlusive matter in a manner which permits the dilation balloon to become operatively positioned adjacent the occlusive lesion. In view of this problem, there exists a need in the art for development of a balloon dilation catheter having an onboard ablation component for partially ablating, or opening a channel through the offending lesion, thereby facilitating operative advancement and positioning of the dilation balloon within the offending lesion.
Another problem associated with balloon dilation angioplasty as well as other intravascular ablation or surgical procedures (e.g. laser ablation or atherectomy) is the occurrence of constrictive vasospasm in the affected blood vessel during or immediately after the procedure. Severe vasospasm may result in complete occlusion of the affected blood vessel, thereby presenting an acute clinical emergency.
The occurrence of vasospasm can result in ischemia or infarction and, at last theoretically, may promote intravascular thrombus formation. See, Fischell, T. A., Derby, G., Tse, T. M. and Stadius, M. L.; Coronary Artery Vasoconstriction Routinely Occurs After Percutaneous Transluminal Coronary Angioplasty: A Quantitative Arteriographic Analysis; Circulation; Vol 78; 1323-1334 (1988). One means of treating vasospasm is to administer vasorelaxant pharmacologic agents to prevent or relieve the untoward vasospasm. Recent observations have indicated that the administration of ultrasonic energy to the blood vessel, in the region of the vasospasm, may effect rapid vasorelaxation without the need for administration of pharmacological agents. (Abstract) Chokahi, S. K. , et al. ULTRASONIC ENERGY PRODUCES ENDOTHELIUM-DEPENDENT VASOMOTOR RELAXATION IN VITRO, Abstracts of the 62nd Scientific Sessions of the American Heart Association (1989). Accordingly, it is desirable to develop ultrasonic devices and methods for preventing or treating vasospasm angioplasty or ablative procedures.